An Assessment of U.S.-Based Electron-Ion Collider Science

Transcription

1 BOARD ON PHYSICS AND ASTRONOMY (BPA) An Assessment of U.S.-Based Electron-Ion Collider Science A study under the auspices of the U.S. National Academies of Sciences, Engineering, and Medicine Gordon Baym and Ani Aprahamian, Co-Chairs The study is supported by funding from the DOE Office of Science. (Further information can be found at:

2 The National Academies of Science, Engineering and Medicine The National Academies produce reports that shape policies, inform public opinion, and advance the pursuit of science, engineering, and medicine. The present report is carried out under the leadership of the Board on Physics and Astronomy (James Lancaster, Director). The BPA seeks to inform the government and the public about what is needed to continue the advancement of physics and astronomy and why doing so is important.

3 Committee on Assessment of U.S.-Based Electron-Ion Collider Science The National Academies of Sciences, Engineering, and Medicine was asked by the U.S. Department of Energy to assess the scientific justification for building an Electron-Ion Collider (EIC) facility. The unanimous conclusion of the Committee is that an EIC, as envisioned in this report, would be a unique facility in the world that would answer science questions that are compelling, fundamental, and timely, and help maintain U.S. scientific leadership in nuclear physics.

4 What is an Electron-Ion Collider? An advanced accelerator that collides beams of electrons with beams of protons or heavier ions (atomic nuclei). Electron-ion center of mass energy ~ GeV, upgradable to ~140 GeV. High luminosity and polarization! 1) highly polarized electrons, E ~ 4 GeV to possibly 20 GeV 2) highly polarized protons, E ~ 30 GeV to some 300 GeV, and heavier ions Brookhaven Jefferson Lab Two possible configurations: Brookhaven Nat l Lab and Jefferson Lab

5 Committee Statement of Task -- from DOE to the BPA The committee will assess the scientific justification for a U.S. domestic electron ion collider facility, taking into account current international plans and existing domestic facility infrastructure. In preparing its report, the committee will address the role that such a facility could play in the future of nuclear physics, considering the field broadly, but placing emphasis on its potential scientific impact on quantum chromodynamics. In particular, the committee will address the following questions: What is the merit and significance of the science that could be addressed by an electron ion collider facility and what is its importance in the overall context of research in nuclear physics and the physical sciences in general? What are the capabilities of other facilities, existing and planned, domestic and abroad, to address the science opportunities afforded by an electron-ion collider? What unique scientific role could be played by a domestic electron ion collider facility that is complementary to existing and planned facilities at home and elsewhere? What are the benefits to U.S. leadership in nuclear physics if a domestic electron ion collider were constructed? What are the benefits to other fields of science and to society of establishing such a facility in the United States?

6 Committee Membership Gordon Baym, Co-Chair (Illinois): theoretical many-particle physics Ani Aprahamian, Co-Chair (Notre Dame): nuclear experiment Christine Aidala (Michigan): Richard Milner (MIT): Ernst Sichtermann (LBNL): Zein-Eddine Meziani (Temple): Thomas Schaefer (NC State U): Michael Turner (Chicago): Wick Haxton (UC Berkeley): Kawtar Hafidi (Argonne): Peter Braun-Munzinger (GSI): Larry McLerran (Washington): Haiyan Gao (Duke): John Jowett (CERN): Lia Merminga (Fermilab): heavy ion experiment high energy electron experiment heavy ion experiment high energy electron experiment theoretical nuclear physics theoretical astronomy, cosmology theoretical nuclear physics high energy electron experiment heavy ion experiment theoretical nuclear physics high energy electron experiment accelerator physics accelerator physics

7 Report Process & Meeting Schedule Four meetings in 2017, plus three conference calls for entire committee, and many smaller conference calls among working groups First meeting Feb. 1-2 Washington Funding agencies, House Science and Technology Committee, NSAC, EIC collider physics, European perspective, RHIC plans Second meeting April Irvine JLab plans, EIC User Group, EIC in China, CERN, gluon and deep inelastic scattering physics Third meeting Sept Woods Hole EIC accelerator technology, EIC computing, gluon saturation Fourth and final meeting: Nov Washington

8 Committee members talking today Gordon Ani Richard Ernst John Thomas Baym Aprahamian Milner Sichtermann Jowett Schaefer Committee at the Academies, Washington D.C.

9 Bottom Line The committee unanimously finds that the science that can be addressed by an EIC is compelling, fundamental, and timely. The unanimous conclusion of the Committee is that an EIC, as envisioned in this report, would be a unique facility in the world that would boost the U.S. STEM workforce and help maintain U.S. scientific leadership in nuclear physics. The project is strongly supported by the nuclear physics community. The technological benefits of meeting the accelerator challenges are enormous, both for basic science and for applied areas that use accelerators, including material science and medicine.

10 Outline of the Report Front Matter Preface Summary Ch 1: Introduction (overview) Ch 2: The scientific case for an electron-ion collider (and how an EIC would do the science) Ch 3: The role of an EIC within the context of nuclear physics in the U.S. and internationally Ch 4: Accelerator science, technology, and detectors needed for a U.S.-based EIC Ch. 5: Comparison of a U.S.-based EIC to current and future facilities Ch. 6: Impact of an EIC on other fields Ch 7: Conclusion and findings Appendixes: Statement of Task; Bios; Acronyms

11 Ch. 2: Basic science to be explored How does a nucleon acquire mass? -- almost 100 times greater than the sum of its valence quark masses. Cannot be understood via Higgs mechanism 1980s Now How does the spin (internal angular momentum) of the nucleon arise from its elementary quark and gluon constituents? Proton spin is the basis of MRI imaging. What are the emergent properties of dense systems of gluons? How are they distributed in both position and momentum in nucleons and nuclei, and how are they correlated among themselves and with the quarks and antiquarks present? What are their quantum states? Are there new forms of matter made of dense gluons?

12 Basic experiments in c.m. energy - luminosity landscape Deeply virtual Compton scattering Deeply virtual meson production

13 Basic experiments in c.m. energy - luminosity landscape Deeply virtual Compton scattering Deeply virtual meson production

14 Ch. 3: The role of an EIC within the context of nuclear physics in the U.S. and internationally Nuclear physics today is a diverse field, encompassing research that spans dimensions from a tiny fraction of the volume of the individual particles (neutrons and protons) in the atomic nucleus to the enormous scales of astrophysical objects in the cosmos. FRIB in construction at MSU will keep us at a leadership position in the world in understanding the behavior of hadrons inside the atomic nucleus Inside hadrons, the interactions of gluons and quarks address the fundamental questions on the origin of mass, spin, and saturation. Quantum Chromodynamics (QCD) physics U.S. Nuclear Science Context for an Electron-Ion Collider U.S. Leadership in Nuclear Science

15 Ch. 4: Accelerator science, technology, and detectors needed for a U.S.-based EIC (Choice of design/site for am EIC was not in our statement of task) Major challenges in accelerator design: o High energy, spin-polarized beams colliding with high luminosity BNL erhic and JLab JLEIC Conceptual Designs o build on existing accelerators in different ways o both require extensive R&D to fully address the science Enabling Accelerator Technologies o Interaction region design, magnet technology o Strong hadron beam cooling (innovative concepts) o Energy Recovery Linacs o Crab Cavity operation in hadron ring o Polarized e,p and 3 He Sources, preservation in accelerators o Simulations of beams in novel EIC operating modes Detector Technologies

16 Ch. 5: Comparison of a U.S.-based EIC to current and future facilities HERA at DESY... A (former) collider of electrons with protons CEBAF at JLab.Electron accelerator to 12 GeV Compass experiment at CERN muons and protons in collisions RHIC Heavy Ion and polarized proton collider LHC at CERN Large Hadron Collider: protons and heavy ions Other Future Electron-Hadron Collider Proposals LHeC FCC-he Future Circular Collider China: possible low energy EIC at HIAF (High Intensity Heavy-Ion Accelerator Facility) Opportunities for future collaborations!!

17 Ch. 6: Impact of an EIC on other fields EIC will sustain a healthy U.S. accelerator science enterprise Maintain leadership in collider accelerator technology Enable new technology essential for future particle accelerators EIC R&D targeted at developing cutting-edge capabilities Workforce Nuclear physicists essential to U.S. security, health & economic vitality About one half of U.S. PhDs in nuclear physics are in QCD Advanced scientific computing Maintaining a competitive high performance computing capability is essential to U.S. scientific leadership Lattice QCD uses the worlds most advanced computers to provide ab initio QCD calculations essential to interpret EIC data Connections to: Condensed matter and atomic-molecular physics High-energy physics Astrophysics

18 Findings The science Finding 1: An EIC can uniquely address three profound questions about nucleons neutrons and protons and how they are assembled to form the nuclei of atoms: How does the mass of the nucleon arise? How does the spin of the nucleon arise? What are the emergent properties of dense systems of gluons? Accelerator Finding 2: These three high-priority science questions can be answered by an EIC with highly polarized beams of electrons and ions, with sufficiently high luminosity and sufficient, and variable, center-of-mass energy.

19 Findings Finding 3: An EIC would be a unique facility in the world, and would maintain U.S. leadership in nuclear physics. Finding 4: An EIC would maintain U.S. leadership in the accelerator science and technology of colliders, and help to maintain scientific leadership more broadly. Finding 5: Taking advantage of existing accelerator infrastructure and accelerator expertise would make development of an EIC cost effective and would potentially reduce risk. Finding 6: The current accelerator R&D program supported by the Department of Energy is crucial to addressing outstanding design challenges.

20 Findings Finding 7: To realize fully the scientific opportunities an EIC would enable, a theory program will be required to predict and interpret the experimental results within the context of QCD, and further, to glean the fundamental insights into QCD that an EIC can reveal. Finding 8: The U.S. nuclear science community has been thorough and thoughtful in its planning for the future, taking into account both science priorities and budgetary realities. Its 2015 Long Range Plan identifies the construction of a high luminosity polarized Electron Ion Collider (EIC) as the highest priority for new facility construction following the completion of the Facility for Rare Isotope Beams (FRIB) at Michigan State University. Finding 9: The broader impacts of building an EIC in the U.S. are significant in related fields of science, including in particular the accelerator science and technology of colliders and workforce development.

21 Bottom Line (again) The committee unanimously finds that the science that can be addressed by an EIC is compelling, fundamental, and timely. The unanimous conclusion of the Committee is that an EIC, as envisioned in this report, would be a unique facility in the world that would boost the U.S. STEM workforce and help maintain U.S. scientific leadership in nuclear physics. The project is strongly supported by the nuclear physics community. The technological benefits of meeting the accelerator challenges are enormous, both for basic science and for applied areas that use accelerators, including material science and medicine.

22 QUESTIONS and ANSWERS

23 Extra slides

24 The Report Process Stages: 1) Defining the study. 2) Committee selection and approval 3) Committee meetings, gather information and write the report 4) Report review via Report Review Committee ~30 members 5) Release of report to public (TODAY)